Comments on absolute and convective instabilities

>Absolute or convective evolutions of instabilities can produce very different signatures of observed radiation from unstable plasmas. This is particularly useful in space plasmas when correlating experimentally observed emissions with theoretical models describing the source regions. A letter has questioned the basis and usefulness of the theory of absolute and convective instabilities by using some singular examples. The arguments put forth by these authors, based upon their singular examples, are misleading. Furthermore, the notion of a time-asymptotic limit is treated in an imprecise manner by these authors. Here, the authors point out the misconceptions in the arguments put forth by Oscarsson and Roennmark [1986] that question the validity and usefulness of the well-known theory of absolute and convective instabilities. The solid basis of the well-known theory is clarified